Electronic information systems may help ameliorate one of the most important problems in health care, the difficulty that health professionals have in acquiring timely access to the information required to give patients optimum management. Many studies have shown that physicians have difficulty in collecting and interpreting information, in keeping up to date, and in applying information. Studies have also shown that physicians prefer print sources when they lack information but, that, in practice, most questions go unanswered because immediate information sources are inadequate, meager selection of journals and disorganized reprint files. Current electronic medical literature databases can provide virtually instant access from clinic and bedside to a vast array of updated information. For example, MEDLINE (from the U.S. National Library of Medicine) contains over 4 million citations, many with abstracts, BRS/Saunders, Colleague, a somewhat more expensive service, has the MEDLINE files plus an expanding number of fulltext journals and textbooks. Thus, users can do "one stop" electronic shopping for information. The Canadian Hospital Association offers both MEDLINE and Colleague, plus other services. We propose to make this service available in clinics and on the wards of McMaster University Medical Center for an 8 month trial period to determine: 1. frequency and patterns of use by clinicians at different levels of training and with different background characteristics; 2. clinical problems that give rise to use; 3. expertise of clinicians in constructing searches in comparison with 'expert' searchers of two types: a) clinicians experienced with online searching; b) librarians who act as search intermediaries in the Health Science Library; 4. extent to which clinicians perceive that the services meets their expectations, provides useful information and influences clinical decision-making; 5. extent to which searches lead to the retrieval of articles that report studies that are both relevant to the clinical problem and scientifically sound; 6. frequency of literature citation in charts supporting clinical decisions; 7. effect of introducing user fees, after an introductory period of free use, on the frequency and efficiency of searches and the types of search services used.